我正在初始化一个优先级队列,如:
strategy = new FuelPriority();
incoming = new PriorityQueue<Vehicle>(1, strategy);
我的Comparator类的代码是:
public class FuelPriority implements Comparator<Object> {
public int compare(Object o1, Object o2) {
Vehicle a1 = (Vehicle) o1;
Vehicle a2 = (Vheicle) o2;
return Integer.compare(a1.getFuelLevel(), a2.getFuelLevel());
}
}
运行模拟后,元素根本没有排序 - 它们是随机的;我在FuelPriority
类的比较方法中设置了断点,但根本没有调用它。
我在这里错过了什么吗?
答案 0 :(得分:3)
除了您的代码上的拼写错误,它对我有用。
import java.util.Comparator;
import java.util.PriorityQueue;
public class StackOverflow
{
public static void main(String[] args)
{
FuelPriority strategy = new FuelPriority();
PriorityQueue<Vehicle> incoming = new PriorityQueue<Vehicle>(4, strategy);
incoming.add(new Vehicle("car1", 10));
incoming.add(new Vehicle("car2", 20));
incoming.add(new Vehicle("car3", 15));
incoming.add(new Vehicle("car4", 1));
// to retrieve the elements in order
while (!incoming.isEmpty()) {
System.out.println(incoming.poll());
}
}
}
class FuelPriority
implements Comparator<Object>
{
public int compare(Object o1, Object o2)
{
Vehicle a1 = (Vehicle)o1;
Vehicle a2 = (Vehicle)o2;
return Integer.compare(a1.getFuelLevel(), a2.getFuelLevel());
}
}
class Vehicle
{
private String name;
private int fuelLevel;
public Vehicle(String name, int fuelLevel)
{
this.name = name;
this.fuelLevel = fuelLevel;
}
public int getFuelLevel()
{
return fuelLevel;
}
@Override
public String toString()
{
return name + "=" + fuelLevel;
}
}
答案 1 :(得分:2)
API表示不保证PriorityQueue迭代器以任何特定顺序遍历优先级队列的元素。它只保证轮询,删除,查看和元素访问队列头部的元素(最少元素)